Improved performance of a heterogeneous weld joint of copper-steel AISI 1045 obtained by rotary friction using a metal powder insert

Rotary friction welding is a means of assembly used in different fields even to perform heterogeneous welds. These latter obtained by conventional techniques in the liquid phase present several difficulties. The fragility of the bead is not only due to the induced metallurgical transformations, but also to the morphology of the interface serving as a physical junction. Then, the hard and brittle intermetallic compounds formed in a non-equilibrium matrix frequently affect the quality and performance of the solder joint. However, the metallurgical bonds obtained by interdiffusion of chemical elements on either side of the interface, in the solid state, often exhibit satisfactory solutions. One of our objectives in the present work consists in attenuating the extent of these undesirable intermetallic compounds, by diluting them in a heterogeneous solution, composed of the two materials to be assembled. It is worth noting that a concentration of stresses may be due not only to a geometric or structural defect, but also to a sudden change of material properties. To avoid such a situation, we propose the technique of inserting a mixture of metallic powders, between the two materials to be joined by rotary friction. This technique consists of going from one material to another in a continuous and progressive way by crossing the powder mixture between them. This allows improvement of certain mechanical and metallurgical characteristics of the solder joint. This technique is implemented and a microstructural and mechanical characterization is carried out on the obtained welded joints between commercial pure copper and carbon steel.